Embodiments in accordance with the present invention relate to generation of a defect map for registering positions of defects on a medium.
The devices using an optical disk, a magnetic tape, or the like, are known as medium devices. Among them, a hard-disk drive (HDD) is most commonly used as a storage device in computers, and the HDD is one storage device essential for current computer systems. In addition, the use of the HDD is not limited to computer systems, and because of its excellent characteristics, is increasingly expanding into such products as moving-picture recording/reproducing devices, car navigation systems, hand-held phones, and removable memories used in digital cameras.
For such a HDD, high reliability is requested. Accordingly, its manufacturing processes include the process of testing for defects on the surface of a magnetic disk. One of magnetic disk tests is a test performed by the manufactured HDD itself to detect defects on magnetic disks in the HDD. For example, the HDD identifies defects on the magnetic disks by writing data onto the data tracks of each magnetic disk and reading out the written data.
This test is performed on the overall area of each recording surface of the magnetic disks of the HDD. Defective sectors that have been detected are registered on a primary defect map (PDM). The HDD does not access and skips the defective sectors that have been registered on the primary defect map.
Several types of formats are known as PDM formats. In one typical PDM format, one defective sector is registered in one entry (hereinafter, called “single-sector entry format”). In this format, the number of entries and the amount of data in the PDM increase in proportion to an increase in the number of defective sectors. However, since the memory capacity allocated to the PDM is limited, the number of defective sectors that can be registered on the PDM is also limited.
Accordingly, several other PDM formats have been proposed for registering a larger number of defective sectors in a limited memory capacity. A format proposed in Patent Document 1 (Japanese Laid-Open Patent Application Publication No. 2001-23310), for example, is a format in which a one-dimensional defective sector array consisting of multiple data sectors is registered in one entry (hereinafter, called “multi-sector entry format”). A format proposed in Patent Document 2 (Japanese Laid-Open Patent Application Publication No. 2002-268829) is a format in which a two-dimensional array consisting of multiple sectors is registered in one entry (hereinafter, called “two-dimensional entry format”).